Add V8_ALIGNOF() and use that in lazy-instance.h.

src/lazy-instance.h

Index: src/lazy-instance.h
diff --git a/src/lazy-instance.h b/src/lazy-instance.h
index 9d68b8cacce0f0f4815f6a5940716df0ddf83bbb..cdde2255ff19be0ef92c00f40916249769449665 100644
--- a/src/lazy-instance.h
+++ b/src/lazy-instance.h
@@ -111,17 +111,9 @@ struct LeakyInstanceTrait {
 
 // Traits that define how an instance is allocated and accessed.
 
-// TODO(kalmard): __alignof__ is only defined for GCC > 4.2. Fix alignment issue
-// on MIPS with other compilers.
-#if defined(__GNUC__) && (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ > 2))
-#define LAZY_ALIGN(x) __attribute__((aligned(__alignof__(x))))
-#else
-#define LAZY_ALIGN(x)
-#endif
-
 template <typename T>
 struct StaticallyAllocatedInstanceTrait {
-  typedef char StorageType[sizeof(T)] LAZY_ALIGN(T);
+  typedef char StorageType[sizeof(T)] V8_ALIGNAS(V8_ALIGNOF(T));
 
   static T* MutableInstance(StorageType* storage) {
     return reinterpret_cast<T*>(storage);
@@ -133,8 +125,6 @@ struct StaticallyAllocatedInstanceTrait {
   }
 };
 
-#undef LAZY_ALIGN
-
 
 template <typename T>
 struct DynamicallyAllocatedInstanceTrait {